This invention relates to high density thermoset foams of acrylic polymers and to processes for preparing them. Thermoset foams of acrylic polymers are known to be useful in flotation parts, furniture and a wide variety of other structural applications. Such foams are normally prepared by irradiating acrylic ester copolymers as described in J. Cellular Plastics, pp. 38-49 (January, 1967); by polymerizing a terpolymer of acrylonitrile, methacrylic acid and acrylamide with urea in the presence of an azo catalyst as described in British Pat. No. 1,045,229; or by polymerizing acrylic monomer(s) in the presence of aluminum alkyl-oxygen complexes as described in U.S. Pat. Nos. 3,172,868 and 3,293,198.
Heretofore, rigid thermoset foams of acrylic polymers having good heat resistance and solvent resistance have not been prepared by reacting a hydroxy-functional acrylic polymer with an aminoplast resin in the absence of an added blowing agent.